In general, a small-sized camera module is mounted in mobile terminals such as smartphones. Such a module often has an auto-focusing function for automatically focusing at the time of capturing a subject and a hand-shake correction function (OIS: Optical Image Stabilization) for reducing irregularities of an image by correcting hand shake (vibration) caused at the time of capturing an image.
As a hand-shake correction method, a module tilt method is known in which an imaging module is integrally tilted (for example PTL 1). The imaging module is a module having a lens part and an imaging device (for example, a charge coupled device (CCD)), which may be provided with an auto-focusing actuator.
In the following descriptions, the auto-focusing actuator is referred to as “AF actuator,” and the hand-shake correction actuator is referred to as “OIS actuator.”
FIG. 1 is an external view illustrating an exemplary camera module of a traditional module tilt type. FIG. 2 is an exploded perspective view illustrating the exemplary camera module of a traditional module tilt type.
As illustrated in FIGS. 1 and 2, camera module 2 of a traditional module tilt type includes fixing part 21, movable part 22, elastic supporting part 23, imaging module 24, and shake detection part 25. An OIS actuator is composed of fixing part 21, movable part 22, and elastic supporting part 23.
Fixing part 21 includes base member 211, coil part 212, and OIS print wiring board 213. Coil part 212 is disposed on base member 211. OIS print wiring board 213 feeds power to coil part 212, and outputs a detection signal of shake detection part 25 to a control part.
Movable part 22 includes yoke 221, magnet part 222, top plate 223, and module guide 224. Yoke 221 and magnet part 222 are disposed in respective housing sections formed in top plate 223. Module guide 224 is fixed to top plate 223. Imaging module 24 is fixedly disposed in a space sandwiched between a pair of module guides 224.
Elastic supporting part 23 has a biaxial gimbal mechanism, and movable part 22 (top plate 223) is fixed to an outer gimbal. Elastic supporting part 23 is disposed at an approximate center of base member 211 in a floating fashion, and fixed by stopper 231. Elastic supporting part 23 supports movable part 22 such that movable part 22 can rotationally sway around the X axis and the Y axis orthogonal to the optical axis (Z axis), that is, elastic supporting part 23 supports movable part 22 such that movable part 22 can be tilted.
Shake detection part 25 is composed of a gyro sensor that detects the angular velocity of imaging module 24, for example. Shake detection part 25 is fixed to a side surface of module guide 224 of movable part 22. The detection signal of shake detection part 25 is output to the control part through OIS print wiring board 213 that constitutes fixing part 21.
An OIS voice coil motor (VCM) is composed of coil part 212 and magnet part 222. That is, when a current flows through coil part 212, a Lorentz force is generated at coil part 212 by interaction between the magnetic field of magnet part 222 and a current flowing through coil part 212 (Fleming's left hand rule). Since coil part 212 is fixed, a reactive force is exerted on magnet part 222. This reactive force is the driving force of the OIS voice coil motor. Movable part 22 rotationally sways until the driving force of the OIS voice coil motor and the restoration force (returning force) of elastic supporting part 23 become equivalent to each other. In this manner, shift of the optical axis due to hand shake is corrected, and the orientation of the light axis is kept at an orientation.